Influence of Alumina Precursors on Microstructure and Creep Behavior of Sol-Gel Derived Mullite Ceramics
| Autor: | Emilija Tkalčec, Helmut K. Schmidt, Hrvoje Ivanković, Rüdiger Rein |
|---|---|
| Přispěvatelé: | Ovecoglu, Lutfi, Mandal, Hasan |
| Rok vydání: | 2004 |
| Předmět: |
Boehmite
Materials science Ausgangsmaterial Sintering Mullite Mikrostruktur law.invention Sintern law General Materials Science Ceramic Composite material Crystallization Sol-Gel-Verfahren Sol-gel Rasterelektronenmikroskop Mullit Mechanical Engineering Microstructure Grain size Creep resistance sol-gel mullite microstructure creep Creep Mechanics of Materials visual_art visual_art.visual_art_medium Aluminium oxydatum ddc:620 |
| Zdroj: | Key Engineering Materials. :997-1000 |
| ISSN: | 1662-9795 |
| DOI: | 10.4028/www.scientific.net/kem.264-268.997 |
| Popis: | The effect of alumina precursors on microstructure, sintering and creep behavior of sol-gel derived mullite ceramics was studied by scanning and transmission electron microscopy (SEM, TEM and HRTEM), dilatometry and measuring the creep resistance in 4-point bending mode. When aluminum nitrate nonahydrate was used as the precursor, elongated crystals (with longer axis about 5-7 mm) were embedded into a matrix of polyhedral much smaller grains. This morphology was due to overlapping of mullite crystallization and viscous flow sintering. Equiaxial mullite grains with 1.3 μ m mean sizes were obtained using boehmite (γ -AlOOH) as alumina precursor. Transient alumina formed in situ by the decomposition of boehmite shifted the mullite formation above the sintering temperature, and allowed the formation of equiaxial mullite grains. Four-point bending creep behavior of mullite ceramics was studied in the temperature range of 1320-1400°C under the stresses between 40 and 160 MPa. The higher creep rate and the smaller activation energy (Q= 606± ; ; ; ; 33 kJ/mol) exhibited the sample with bimodally distributed grain sizes, whereas a smaller creep rate and the higher activation energy (Q=743± ; ; ; ; 18 kJ/mol) were obtained for mullite ceramic with monomodally distributed grain sizes. |
| Databáze: | OpenAIRE |
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